import java.util.List;

public class MyLinkedList implements IList{
    static class ListNode{
        public int val;
        public ListNode next;
        public ListNode prev;
        public ListNode(int val){
            this.val=val;


        }

    }
    public ListNode head;
    public ListNode last;
    @Override
    public void addFirst(int data) {
        ListNode node=new ListNode(data);
        if (head==null){
            head=node;
            last = node;
        }
        else {
            node.next=head;
            head.prev=node;
            head=node;

        }
    }

    @Override
    public void addLast(int data) {
        ListNode node=new ListNode(data);
            if(head==null){
                head=node;
                last=node;
            }
            else {
                last.next = node;
                node.prev = last;
                last = node;
            }
            }


    @Override
    public void addIndex(int index, int data) {
        int len = size();
        // 检查index是否合法
        if(index < 0 || index > len) {
            //可以抛出自定义的异常
            System.out.println("index位置不合法："+index);
            return;
        }
        if(index == 0) {
            addFirst(data);
            return;
        }
        if(index == len) {
            addLast(data);
            return;
        }
        ListNode cur = findIndex(index);
        ListNode node = new ListNode(data);
        node.next = cur;
        cur.prev.next = node;
        node.prev = cur.prev;
        cur.prev = node;

    }
    private ListNode findIndex(int index) {
        ListNode cur = head;
        while (index != 0) {
            cur = cur.next;
            index--;
        }
        return cur;
    }

    @Override
    public boolean contains(int key) {
        ListNode cur=head;
        while (cur!=null){
         if (cur.val==key){

            return true;
        }
    cur=cur.next;
    }
        return false;
    }

    @Override
    public void remove(int key) {
        ListNode cur = head;
        while (cur != null) {
            if(cur.val == key) {
                if(cur == head) {
                    head = head.next;//head == null
                    if(head == null) {
                        last = null;
                    }else {
                        head.prev = null;
                    }
                }else {
                    cur.prev.next = cur.next;
                    if(cur.next == null) {
                        last = last.prev;
                    }else {
                        cur.next.prev = cur.prev;
                    }

                }
                return;
            }else {
                cur = cur.next;
            }
        }
    }

    @Override
    public void removeAllKey(int key) {
        ListNode cur = head;
        while (cur != null) {
            if(cur.val == key) {
                if(cur == head) {
                    head = head.next;//head == null
                    if(head == null) {
                        last = null;
                    }else {
                        head.prev = null;
                    }
                }else {
                    cur.prev.next = cur.next;
                    if(cur.next == null) {
                        last = last.prev;
                    }else {
                        cur.next.prev = cur.prev;
                    }
                }
            }
            cur = cur.next;
        }
    }

    @Override
    public int size() {
        ListNode cur = head;
        int count = 0;
        while (cur != null) {
            count++;
            cur = cur.next;
        }
        return count;
    }


    @Override
    public void clear() {
        head = null;
        last = null;
    }

    @Override
    public void display() {
        ListNode cur=head;
        while (cur!=null){
            System.out.print(cur.val+" ");

            cur=cur.next;
        }
        System.out.println();
    }
}
